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Duct Sealing

Keep heated and cooled air in ducts

The ducts for a forced-air heating  and air-conditioning system can  be one of your home’s biggest energy  wasters, especially if those ducts  run through unheated or uncooled  spaces (like attics or crawl spaces). Properly sealed ducts can deliver  heated/cooled air where you need  it, instead of leaking out where  you don’t. This allows your furnace/  air conditioner to work less  to make you comfortable.

  • Check the ducts for air leaks. Repair leaking joints first with sheet-metal screws; then seal joints with either latex-based mastic with embedded fiberglass mesh or metal/ foil tape (UL 181). Don’t use plastic or cloth duct tape because it will harden, crack, and lose its adhesion.
  • Wrap ducts in attics/crawl spaces with special duct insulation; don’t use leftover insulation from other jobs. Seal all insulation joints with the appropriate tape.
  • Make sure ducts fit tightly to the register openings in floors and walls; if they don’t, seal them with caulk.
  • Seal return ducts, too, so you won’t be breathing basement or crawl space air.
  • Make sure registers and baffles are adjusted properly to distribute heated and cooled air to where you need it. For example, in the winter close registers in unused rooms.
  • Don’t confuse duct-sealing with duct-cleaning! There are no energy-related benefits to duct-cleaning.